Conventionally, most domestic liquid detergents and liquid fabric conditioning or fabric softener compositions make use of thickening properties of surfactant ingredients or added salts to come to a desired rheology. The last decade, however, there is a growing need to come to formulations that are physically and rheologically stable at ambient conditions for at least a month or so. Such formulations generally contain specific thickeners in amounts leading to the desired viscosities and giving suitable stabilities.
WO 90/12862 (BP Chemicals Ltd.) discloses aqueous based fabric conditioning formulations comprising a water dispersible cationic softener and as a thickener a cross-linked cationic polymer that is derivable from a water soluble cationic ethylenically unsaturated monomer or blend of monomers, which is cross-linked by 5 to 45 ppm of a cross-linking agent comprising polyethylenic functions. More in particular, these cationic polymers are formed from monoethylenically unsaturated monomer that is either a water soluble cationic monomer or is a cationic blend of monomers that may consist of cationic monomers alone or may consist of a mixture of cationic and non-ionic monomers in the presence of a cross-linking agent. Polymeric thickeners which are in accordance with this prior art publication are referred to herein in the description and Examples for comparative purposes; they are usually referred to as “BP polymer”.
The preferred amount of cross-linking agent used in the polymerization is said to be selected in such a way that the Ionic Regain reaches a peak or plateau and preferably is between 10 and 25 ppm.
A commercial product covered by said WO 90/12862 is a cross-linked cationic copolymer of about 20% acrylamide and about 80% of trimethylammonioethylmethacrylate salt cross-linked with 5-45 ppm methylene bis acrylamide (MBA). The cross-linked polymer is supplied in a liquid form as an inverse emulsion in mineral oil. It is referred to in the present description as the “BP polymer”.
In EP-A-0 799 887 liquid fabric softening compositions are described which are said to exhibit an excellent viscosity and phase stability as well as softness performance, which compositions comprise: (a) 0.01-10 wt. % of a fabric softener component, (b) at least 0.001% of a thickening agent selected from the group of (i) associative polymers having a hydrophilic backbone and at least two hydrophobic groups per molecule attached to the hydrophilic backbone, (ii) the cross-linked cationic polymers described in the above-mentioned WO 90/12862, cross-linked by 5-45 ppm of cross-linking agent comprising polyethylenic functions and (iii) mixtures of (i) and (ii), and (c) a component capable of sequestering metal ions.
In Research Disclosure page 136, no. 429116 of January 2000, SNF Floerger has described cationic polymeric thickeners that are useful in fabric softeners. The thickeners described are branched and/or cross-linked cationic polymers formed from monoethylenically unsaturated monomers being either water soluble cationic monomers or blends of cationic monomers that may consist of cationic monomers alone or may comprise a mixture from 50-100% cationic monomer or blend thereof and from 0-50% of non-ionic monomers in the presence of a cross-linking agent in an amount of 60 to 3000 ppm and of chain transfer agent in an amount of between 10 and 2000 ppm. The cationic monomers are selected from the group of dimethylaminopropyl methacrylamide, dimethylaminopropylacrylamide, diallylamine, methyldiallylamine, dialkylaminoalkylacrylate and methacrylate, dialkylaminoalkyl acrylamide or methacrylamide, derivatives of the previously mentioned monomers or quaternary or acid salts thereof. Suitable non-ionic monomers are selected from the group consisting of acrylamide, methacrylamide, N-alkyl acrylamide, N-vinyl pyrrolidone, vinylacetate, vinyl alcohol, acrylate esters, allyl alcohol, and derivatives thereof. The cross-linking agents are methylene bisacrylamide and all diethylenically unsaturated compounds.
U.S. Pat. No. 4,806,345 teaches personal care compositions which have as a thickening agent a cross-linked cationic vinyl addition polymer. The personal care compositions include water, at least one cosmetically-active agent and such a thickening agent that is preferably derived from the polymerization of a cationic vinyl addition monomer, acrylamide, and 50-500 ppm of a difunctional vinyl addition monomer for cross-linking purposes. Preferred embodiments described in U.S. Pat. No. 4,806,345 only differ from the preferred products of WO 90/12862 in that more (of the same) cross-linking agent is used in the polymerization reaction.